AR-10, LR-308, and how many others are there?

Discussion in 'AR15/10 Rifles' started by dwhunts, Oct 20, 2013.

  1. dwhunts

    dwhunts Well-Known Member

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    I am reasonably certain my next project is gonna be a big AR. This is the beginning, I know there are several different variations of the "AR-10, but that's about all I know. Other than it will be in 7mm SAUM, it will have a heavy 28 or 30 inch barrel, and of course accuracy is the most important attribute. (Disclaimer) I am not now, nor do I plan to shoot "1000 yard bench rest competition." So all you bench rest types, go find another thread to unleash your negative rhetoric on. With that being said, any helpful advice will be greatly appreciated. What I have in mind is a rifle capable of taking any antlered critter in North America at extended ranges.
     
  2. hunterbob

    hunterbob Well-Known Member

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    I got the DPMS Oracle 18" barrel .308 and I love the rifle and shoot pigs and yotes with it within 200 yds
     

  3. dwhunts

    dwhunts Well-Known Member

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    I forgot to mention. I'll be building at least the lower myself.
     
  4. MudRunner2005

    MudRunner2005 Well-Known Member

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    LWRC REPR 18" or 20" spiral-fluted barrel.
     
  5. c_bass16

    c_bass16 Well-Known Member

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    The number of makers that do proprietary stuff with the "large frame" AR's is pretty extensive since there is no "mill spec standard" so to speak.

    The AR10, LR308, SR25, LAR-8 are the ones that come to mind first.

    Of all the models to choose from...these are the ones I would consider brand specific for parts. Just about everything else will mate up to one of these 4.

    The Armalite rolls with the likes of Noveske compatibility but they have offered a 2nd model option for use with DMPS/SR25 Mags...the uppers are stil only going to run on Armalite/Noveske

    The LR308 I would consider to be the most common platform. 95% of companies that make a billet lower, design it for the LR308 style uppers.

    The SR25 is kind of a hybrid. It has the appearance of the Armalite, but the guts of the DPMS. (actually DPMS has KAC guts, but that's not the point)

    And the LAR-8 is just all kinds of proprietary and I don't know what fits it.

    For the caliber choice you've got...you're going to have a hard time finding someone build it for you, and I wish you luck. It's going to be expensive and I would highly doubt that the one man I know of with experience doing the build, will actually build one to those specs...but as I said...good luck with the project.


    And just to clarify...what do you consider "extended ranges" and what do you feel the 7mmSAUM and 28+ barrel will do to help you achieve that kill shot?
     
  6. dwhunts

    dwhunts Well-Known Member

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    c_bass16 I knew you'd come through for me on this one. I almost just messaged you.

    What do you know about these guys?

    Rifle Accuracy Systems Inc Custom Accurate Rifles Barrel Conversions Ruger Mini Remington 700 7400 750 AR10 AR15

    I was thinking about them for the upper.

    As far as extended range. If you remember, I built my .25 WSSM for a 500 yard rifle. I'm planning this one to go beyond that to about a 1000. Some of the places I hunt in Northwest Oklahoma are similar to what you hunt up there in the great white north. Wide open prairies with some big hills interspersed. 300 pound whitetails and some slightly bigger mule deer.

    I was thinking the longer barrel would give me back some of the velocity I'll undoubtedly loose by having to seat the heavier bullets deeper, to fit in the mag. What do you think?

    As far as the 7mm, just better BC's for bullet weight compared to the .30.
     
  7. c_bass16

    c_bass16 Well-Known Member

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    Yes, Carl at Accuracy Systems is the man to talk to when looking for a SAUM in the AR10 platform, but you're going to have to twist his arm to get him to build a 24" upper. The last I heard, his recommendation was that "IF" he does a 7mm SAUM...that it would be more toward the 20" length. As I said, good lucking asking him about the 28"
    This isn't as much of an issue as you'd think it would be.

    You're going to have PLENTY of energy from a bullet that size, going that speed anyway. It's UNMATCHED in the AR10 platform.
    Being able to consistently hit MOA targets on your first shot is where things get interesting anyway.

    You're "probably" only going to be able to run something like the 168gr VLD bullets at mag length without having seating depth issues anyway. And that's a best case scenario. Something like the 162Amax would probably even be best suited due to the relationship of high bc to weight ratio.

    For example, if you run the 162Amax at a conservative 3050fps from a 24" barrel, you're looking at 23 MOA of elevation (6.6 mil) at 1000 yds and you're still carrying OVER 1000 lbs of energy. (at my bp of roughly 28.45 on most days)

    Trying to seat something like a 180 VLD is probably possible, but you're going to run into the ogive getting way down at the case mouth and that's usually too deep to get the accuracy you usually want from a VLD. It's to much of a jump to the lands.
    You can do the math with any bullet you want to see how much seating depth you'll have to work with.

    Typical mag length is 2.800"
    7mmSAUM Case length is 2.035"
    A 180 VLD is 1.525" total and .825" from the base to ogive leaving .7" from the ogive to the tip.

    If you add .7 (ogive to tip) to the length of a case, you're looking at a COAL of 2.735" if you seat a 180 VLD to so the ogive is at the case mouth (not recommended)...which only leaves you .065" to play with seating depth before you're out of mag length.

    So it's possible, but not likely for accuracy. 168 VLD's will be a little better, but I still feel the 162 Amax to be about the ideal bullet for that platform.

    Also, using a powder like RL17...you're going to hit pressure signs, long before you actually run out of case capacity, so seating a heavy bullet deeper doesn't really correlate to loss of velocity in the semi-auto.
    With other powders, that may not be true.

    I purchased a 300 SAUM Armalite Upper a while back and I've been happy as a pig in shat ever since. I've had 3 different bullets (185, 190 and 210 VLDs all shooting around 1/2 MOA) and I've take two of those rounds out to beyond a mile so far.
    Longest game KO is 930 yds and I would have no hesitation in going out to 1200 or so.
    With the .30 cal 190s VLDs that I'm currently running...I'm carrying almost the same energy at 1000 yds, that you could potentially get with the 162 Amax at the same range. So you're correct in the 7mm ballistics...it will just depend on what bullet ultimately get to shoot the best.

    I've been planning to get a 2nd upper in 7mmSAUM built for 2 years now and just haven't gotten around to it.
     
  8. dwhunts

    dwhunts Well-Known Member

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    Would I be better off to just buy an LR308 and re-barrel it in .284 Win.? Seems like a hell of a lot less trouble, and I wouldn't give up much velocity. Even if I have to use the lighter bullets, I think I can get it done out to 800. Brass is pretty readily available, as well as load data.
     
  9. c_bass16

    c_bass16 Well-Known Member

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    Better off?
    Not as far as ballistics go. In fact, you'll probably be worse off, simply because the case is longer, and you'll be even less restricted to shorter lighter bullets.

    You may be better off in that you won't have to change the bolt face, but since the shoulder is farther forward than a .308 case...you're going to have to modify all your mags as well. (you'll have to remove the mag ribs)

    The only positive you have with choosing the .284Win is that you don't have to change the bolt face...but that's a moot point as you're not the one doing the changing anyway.

    In the semi-auto AR10 style platform, the SAUM is unmatched. I would venture to say that it's even going to outperform the WSM due strictly to mag restrictions and bullet choice.
     
  10. dwhunts

    dwhunts Well-Known Member

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    Man... The rabbit hole just keeps getting deeper and deeper don't it. I'm starting to think I may be better off to shelve this idea and see how the market goes. Hell, the way the AR market is going we may have ultra mag ARs in no time. I think I'll just enjoy my .25 WSSM for now. It'll do anything I am likely to need done anyway. After deer season I need to do some load development for it anyway. Thanks for the advice.
     
  11. nitrousmudbogger

    nitrousmudbogger Well-Known Member

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    There are ar's in calibers over 308's now
     
  12. MudRunner2005

    MudRunner2005 Well-Known Member

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  13. dwhunts

    dwhunts Well-Known Member

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    Thank you, for bringing this to my attention! That is awesome! I wouldn't want it in 300 win mag, but they're just scratching the surface of the capabilities of that platform. I understand. They have to cater to the military first. Not that the 300 couldn't do what I want. It could, and do it well. I have, however, swore off belted cases for ever. To me a belt on a case is like a vestigial tail on a human. It just isn't needed anymore. We've evolved past needing it. (If anyone out there has a vestigial tail, I meant no offense. They do call them "vestigial" though.)

    Again. Thank you. This illustrates the exact reason I am on this forum.
     
  14. c_bass16

    c_bass16 Well-Known Member

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    I'm still not quite sold on the OMEN, not for the price point they're looking for.
    It's not exactly outlandish, but for the price of the OMEN and it's ballistics, compared to the price of my 300 SAUM and it's ballistics...I don't see the draw.

    RND Rifles
    have a FINE LIST of semi-autos as well, but again...a bit out of my budget.
    The difference between both the RND and NEMO line, is that they are built on proprietary platforms...for obvious reasons.

    You're right to assume that the market is going to continue to improve, but the caliber restrictions of the AR10 style and the AR15 are going to always come down to the size of the platform and the cartridge your trying to stick into it.

    You're not likely to see anything bigger than the SAUM/WSM in the AR10...specifically because of the .532 bolt face. Anything bigger than that and you're not going to have the strength in the bolt lugs.
    You're also not going to see any longer cases being used because of mag length restrictions.

    The same for the AR15. The WSSM case is easily the limit here, because it required a completely proprietary bolt...not just an opened up bolt face.
    The same with the case length.
    Oly got around the case length restriction with the 22-250, but making proprietary parts and mags to make it work.

    When you get to those levels of modification, you lose the ability to do it at a reasonable cost...which only accentuates the attraction of more standard calibers.